Flume for a filter system including at least one filter having a filter bed that is periodically washed with liquid, gas or a combination thereof

Abstract

A flume for a filter system including at least one filter having a filter bed that is periodically washed with liquid, gas and / or a combination of liquid and gas. The flume includes a chamber having a top wall, a bottom wall, a left sidewall and a right sidewall. The chamber is adapted to receive a liquid, a gas and / or a combination of liquid and gas. Preferably, the flumes includes at least a first inner wall and a second inner wall. Each of the first inner wall and the second inner wall are preferably free of any orifices. The first inner wall is positioned relative to the second inner wall such that an open space is formed between the first inner wall and the second inner wall. The open space creates a first liquid / gas interface upstream of the first inner wall and the second inner wall and a second gas / liquid interface downstream of the first inner wall and the second inner wall when gas and liquid are present in the chamber. The first interface is spaced from the bottom wall of the chamber a distance greater than the second interface.

Description

FIELD OF THE INVENTION[0001]The present invention is directed to a filter system having one or more filter beds that are periodically washed with a liquid, a gas and / or a combination of a liquid and a gas. Where a combination of a liquid and gas is used to wash the filter beds, the liquid and gas can be directed through the filter bed simultaneously or separately. More specifically, the present invention is directed to an improved flume used in a filter system having one or more filter beds that are periodically washed with a liquid, a gas and / or a combination of a liquid and a gas. The present invention can be used in both water and wastewater applications.BACKGROUND OF THE INVENTION[0002]Filter beds formed from one or more layers of filter media have been employed in a variety of known filters for filtering water or wastewater to remove impurities from liquids. For example, filter beds of granular media have been used in upflow filters, downflow filters as well as other type of fi...

AI Technical Summary

Benefits of technology

"The present invention provides a novel and unobvious flume and filter system that can accommodate different washing procedures and flow conditions. The flume includes a chamber with inner walls that create a first liquid / gas interface and a second gas / liquid interface, allowing for a smooth transition between low and high liquid flow rates. The flume also induces laminar flow and reduces preforming of orifices in baffles or stand-pipes. The flume is easy to construct and controls the gas / liquid interface over a wider range of flow conditions. These technical effects make the flume more efficient and effective in filter systems."

Problems solved by technology

One significant problem encountered by prior art devices is their inability to accommodate changes in the washing procedure including changes in the flow rates and changes in the washing fluids.

For example, a washing procedure that employs simultaneous liquid and air washing fluids is highly susceptible to mal-distribution of the washing fluid through the filter bed.

This is undesirable as it limits the area available for the washing liquid resulting in relatively high liquid washing flow velocities down the length of the flume which in turn causes mal-distribution of the washing fluids to the underdrain and ultimately the filter bed.

Forming orifices of the type illustrated in FIG. 1 of the subject specification normally requires expensive formwork to accommodate the air and water wall sleeves that are cast in place.

To be cost effective, the wall sleeves are made using commercially available sizes, which limits the available orifice sizes.

Hence, most designs are not optimal but rather less efficient designs due to the compromise between technical considerations and commercially available materials.

The orifice design disclosed and claimed in U.S. Pat. No. 6,312,611 is also inferior due to its inability to tailor the headloss characteristics over a range of flows.

This is particularly troublesome when the washing procedure includes a first step of concurrent liquid and gas followed by liquid only.

The increase in the flow rate of the washing fluid in the second step dramatically impacts the headloss across the orifice.

This dramatic increase in headloss creates very difficult flow control issues.

Poor flow control will likely result in disruption of the gas / liquid interface within the flume, mal-distribution of the washing fluids, and the undesirable release of uncontrolled air into the underdrain.

These conditions will likely cause structural failures of the underdrain system, disruption of the support gravel, and poor performance.

As is readily evident from the above discussion, the orifice design is inflexible from the design stand-point and the application stand point as the design is limited to commercially available sizes and is unable to accommodate changes in the washing procedure.

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